The present invention relates generally to an apparatus for cutting successive portions from a column of plastic material such as viscous glass.
In the glass forming process, glass is fed from an outlet spout of a feeder bowl to a glass forming machine. A shear mechanism is mounted underneath the feeder bowl to successively cut gobs from the column of glass from the feeder bowl. One type of shear mechanism utilizes a pivoted shear structure wherein shear blades are mounted on swinging arms. In high speed applications, especially, there is a tendency for excessive wear in mechanisms of that type. Further, in double or triple gob applications, the gobs are not cut at exactly the same time. Thus, the gobs will not be delivered to the molds of a given machine section at exactly the same time thereby affecting the forming times.
To overcome the above problems, straight line shearing has been proposed. In straight line shearing, the shear blades advance in a straight line toward the issuing gobs from opposite directions. U.S. Pat. No. 1,642,966 issued to W. J. Miller on Sept. 20, 1927; U.S. Pat. No. 3,435,719 issued to F. J. Wythe on Apr. 1, 1969; and U.S. Pat. No. 3,996,037 issued to F. J. Wythe on Dec. 7, 1976 show examples of straight line shearing. Straight line shearing mechanisms may also be provided with means to adjust the vertical height of either the upper or lower shear blades to adjust the "tension" between opposite blades when they overlap during the cutting stroke. Such an arrangement is shown in U.S. Pat. No. 3,579,319 issued to F. J. Wythe and H. Hoette on May 18, 1971. Additionally, the drop guides for guiding the severed gob during its initial downward movement as it is being separated from the suspended molten glass column may be adjustable toward and away from the suspended column of molten glass as also shown in U.S. Pat. No. 3,579,319.